mc-6 mobile ip

8/14/2019 MC-6 Mobile IP

1/44

Mobile IP


2/44

MOBILE IP

Mobile computing in a true sense will be able to provide an environment where auser will be able to continuously access data and services in a state of mobility.

A data connection between two end-points through TCP lIP network requires a

source IP address, source TCP port and a target IP address with a target TCP

port.

The combination of one IP address of the host system combined with a TCP

port as the identification of a service becomes a point of attachment for an

end-point. TCP port number is application-specific and remains constant. IP

address, on the other hand, is network specific and varies from network to

network.

IP addresses are assigned to a host from a set of addresses. This structure

works well as long as the client is static and is using a desktop computer.


3/44

Let us assume that the user is mobile and is using a laptop with WiFi

As the user moves, the point of attachment will change from one subnet to another

subnet resulting in a change of IP address.

This will force the connection to terminate. Therefore, the question is how do we

allow mobility while a data connection is alive.

The technology to do so is 'Mobile IP,and signifies that, while a user is connected to

applications across the Internet and the user's point of attachment changes

dynamically, all connections are maintained despite the change in underlying network

properties. This is similar to the handoff roaming situation in cellular network.


4/44

Internet Protocal routes packets from a source endpoint to a destination endpoint

through various routers. An IP address of a host can be considered to be a combinationof network address (most significant 24 bits) and the node address (least significant 8

bits).

The network portion of an IP address is used by routers to deliver the packet to the last

router in the chain to which the target computer is attached. This last router then uses

the host portion of the IP address to deliver the IP packet to the destination computer.

The port number is used by the host to deliver the packet to the appropriate

application.

To ensure that an active TCP connection is not terminated while the user is mobile, it is

essential that all of these four identities remain constant.

The TCP ports are application specific and generally constant. However, the IP address

changes from subnet to subnet.

MOBILE IP


5/44

Therefore, to fix this problem mobile IP allows the mobile node to use two IP addresses.

These IP addresses are called home addressand care-of address.

The home address is static and known to everybody as the identity of the host. The

care-of address changes at each new point of attachment and can be thought of as the

mobile node's location specific address.

This is similar to the concept of HLR (Home Location Register) and VLR (Visitor Location

Register) in cellular networks.

When the mobile node is roaming and is attached to a foreign network, the home agent

receives all the packets for the mobile node and arranges to forward them to the mobile

node's current point of attachment.

The network node that is responsible for forwarding and managing this transparency is

known as the home agent.

MOBILE IP


6/44

MobileIP Mobile IP was developed as a means for transparently dealing with problems of mobile

users Enables hosts to stay connected to the Internet regardless of their location

Enables hosts to be tracked without needing to change their IP address

Requires no changes to software of non-mobile hosts/routers

Requires addition of some infrastructure

Has no geographical limitations

Requires no modifications to IP addresses or IP address format

Supports security

Could be even more important than physically connected routing

IETF standardization process is still underway


7/44

Definitions Home Network: Network where the mobile node belongs originally

Home Address: IP address of the mobile node in the home network

(static)

Home Agent: Typically a router on the home network that controls

traffic in that network

Foreign Network: Network different from the home where the

mobile node is connected at the moment.

Foreign Agent: Typically a router on the foreign network. It controls

traffic in that network.

Care-of Address: Temporary IP address assigned to the mobile unit

by the foreign network


8/44

Permanent Address: IP address permanently assigned to the Mobile node

Care-of address: Temporary IP address assigned to Mobile node by

Foreign agent

Correspondent: Node wishing to communicate with Mobile node

Functionality:

Correspondent sends a message addressed to the Permanent address.

This message will arrive to the Home agent. Home agent forwards the

message to Foreign agent.

Foreign agent forwards it to Mobile node.

Mobile node replies directly to Correspondent.

Mobile IP - cont


9/44

Mobile IP -cont

Additional protocols required:

Agent discovery:Mobile node finds the Foreign agent or Home agent

Registration with Home agent: Foreign agent sends Home agent Care-of

address

Indirect routing of Correspondents datagrams:Rules about encapsulating

datagrams forwarded to Mobile node by Home agent


10/44

Mobile IP Entities

Mobile Node (MN) The entity that may change its point of attachment from network to network in the

Internet

Detects it has moved and registers with best FA

Assigned a permanent IP called its home address to which other hosts send packetsregardless of MNs location

Since this IP doesnt change it can be used by long-lived applications as MNslocation changes

Home Agent (HA)

This is router with additional functionality

Located on home network of MN

Does mobility binding of MNs IP with its COA Forwards packets to appropriate network when MN is away

Does this through encapsulation


11/44

Mobile IP Entities contd.

Foreign Agent (FA)

Another router with enhanced functionality

If MN is away from HA the it uses an FA to send/receive data to/from HA

Advertises itself periodically

Forwards MNs registration request Decapsulates messages for delivery to MN

Care-of-address (COA)

Address which identifies MNs current location

Sent by FA to HA when MN attaches

Usually the IP address of the FA

Correspondent Node (CN)

End host to which MN is corresponding (eg. a web server)


12/44

Mobile IP Support Services

Agent Discovery

HAs and FAs broadcast their presence on each network to which they areattached

Beacon messages via ICMP Router Discovery Protocol (IRDP)

MNs listen for advertisement and then initiate registration

Registration When MN is away, it registers its COA with its HA

Typically through the FA with strongest signal

Registration control messages are sent via UDP to well known port

Encapsulationjust like standard IP only with COA

Decapsulationagain, just like standard IP


13/44

Mobile IP Operation

A MN listens for agent advertisement and then initiates registration If responding agent is the HA, then mobile IP is not necessary

After receiving the registration request from a MN, the HA acknowledges and

registration is complete

Registration happens as often as MN changes networks

HA intercepts all packets destined for MN This is simple unless sending application is on or near the same network as the MN

HA masquerades as MN

There is a specific lifetime for service before a MN must re-register

There is also a de-registration process with HA if an MN returns home


14/44

Registration Process


15/44


16/44

Mobile IP Operation contd.

HA then encapsulates all packets addressed to MN and forwards them to FA

IP tunneling

FA decapsulates all packets addressed to MN and forwards them via hardware address(learned as part of registration process)

NOTE that the MN can perform FA functions if it acquires an IP address eg. via DHCP

Bidirectional communications require tunneling in each direction


17/44


18/44

18

Home Network and Home Agent

Home network:permanenthome of mobile(e.g., 128.119.40/24)

Permanent address:address in home network,can alwaysbe used toreach mobilee.g., 128.119.40.186

Home agent: entity that willperform mobility functions onbehalf of mobile, when mobile isremote

wide areanetwork

correspondent

Correspondent:wants to

communicate with mobile


19/44

19

Visited Network and Care-of Address

Care-of-address:address in

visited network.(e.g., 79,129.13.2)

wide areanetwork

Visited network:network inwhich mobile currentlyresides (e.g., 79.129.13/24)

Permanent address:remainsconstant (e.g., 128.119.40.186)

Home agent: entity invisited network thatperforms mobilityfunctions on behalf ofmobile.Correspondent:wants to

communicate with mobile


20/44

IP Mobile Basic Capabilities

Discovery: A mobile unit uses a discovery procedureto identify prospective home agents and foreignagents.

Registration: A mobilenode uses an authenticatedregistration procedure to inform its home agent of itscare-of address

Tunnelling: Tunnelling is used to forward IP

datagrams from a home address to a care-ofaddress.


21/44

Discovery

Need to determine if the node is in its home network

or on a foreign network. This is done through

Advertisement.

A transmission from the home network to a foreignnetwork can occur at any time without notification

to the network layer (IP layer)

discovery for a mobile node is a continuous process.


22/44

Lecture 5: Mobility

Mobile IP: agent discovery

agent advertisement:foreign/home agents advertise serviceby broadcasting ICMP messages(typefield = 9)

RBHFMGVbits

reserved

type = 16

type = 9 code = 0 checksum

router address

standardICMP fields

mobility agentadvertisement

extension

length sequence #

registration lifetime

0 or more care-of-addresses

0 8 16 24

R bit: registrationrequired

H,F bits: homeand/or foreign agent

22


23/44

DiscoveryMove Detection

Mobile nodes may move between networksdue to some handoff mechanism without theIP level being aware of it.

Agent Discovery Process is intended to enablethe agent to detect such move. There are twoalgorithms used for this:

Use of Lifetime Field

Use of Network Prefix


24/44

Move Detection Algorithms

Lifetime Filed:When a mobile node(MN) receives an agent

advertisement from a foreign agent that it is currently using or

that it is now going to register with, it records the lifetime

field as a timer

If the timer expires before the MN receives another agent advertisement fromthe agent, then the node assumes that it lost contact with that agent.

If the MN has received an agent advertisement from another agent, and that

advertisement has not yet expired, the MN can register with this new agent.


25/44

Move Detection Algorithms

Network Prefix: The mobile node (MN) checks

whether any newly received agent advertisement is

on the same network as the nodes current care-of-

address. If it is not, the MN assumes that it has moved and may

register with the agent whose advertisement the mobile

node has just received.


26/44

Registration

Once a mobile node has recognized that it is

on a foreign network and has acquired a care-

of address, it needs to alert a home agent on

its home network and request that the homeagent forward its IP traffic


27/44

Registration

The registration process involves four steps:

1. The mobile node requests the forwarding service by sendinga registration request to the foreign agent that the mobile

node wants to use.2. The foreign agent relays this request to the mobile nodes

home agent.

3. The home agent either accepts or denies the request and

sends a registration reply to the foreign agent.4. The foreign agent relays this reply to the mobile node


28/44

28

Mobility: Registration

Foreign agent knows about mobile

Home agent knows location of mobile

wide area

network

home networkvisited network

1

mobile contactsforeign agent onentering visitednetwork

2

foreign agent contacts home agenthome: this mobile is resident in mynetwork


29/44

29

Mobility via Indirect Routing

wide areanetwork

home

network

visitednetwork

3

2

41

correspondentaddresses packetsusing home addressof mobile

home agent interceptspackets, forwards toforeign agent

foreign agentreceives packets,forwards to mobile

mobile repliesdirectly tocorrespondent


30/44

Lecture 4: Mobility

Indirect Routing: comments

Mobile uses two addresses: permanent address:used by correspondent (hence

mobile location is transparentto correspondent)

care-of-address:used by home agent to forward

datagrams to mobile foreign agent functions may be done by mobile itself

triangle routing:correspondent-home-network-mobile

inefficient when

correspondent, mobile

are in same network

30


31/44

31

Indirect Routing: Efficiency Issues

Mobile uses two addresses

Permanent address: used by correspondent (making

mobiles location is transparent to correspondent)

Care-of-address: used by the home agent to forwarddatagrams to the mobile

Mobile may perform the foreign agent functions

Triangle routing is inefficient E.g., correspondent and mobile in the same network


32/44

32

Mobility via Direct Routing

wide areanetwork

home

network

visitednetwork

4

2

41correspondentrequests, receivesforeign address ofmobile

correspondent forwardsto foreign agent

foreign agentreceives packets,forwards to mobile

mobile repliesdirectly tocorrespondent

3

No longer transparent to the correspondent


33/44

Lecture 5: Mobility

Mobile IP: indirect routing

Permanent address:128.119.40.186

Care-of address:79.129.13.2

dest: 128.119.40.186

packet sent bycorrespondent

dest: 79.129.13.2 dest: 128.119.40.186

packet sent by home agent to foreignagent: apacket within a packet

dest: 128.119.40.186

foreign-agent-to-mobile packet

33


34/44

Tunnelling

Once a mobile node is registered with a home agent,the home agent must be able to intercept IPdatagrams sent to the mobile nodes home address

so that these datagrams can be forwarded viatunnelling

To forward an IP datagram to a care-of-address, the

home agent puts the entire IP datagram into anouter IP datagram. This is a form of encapsulation


35/44

Tunnelling

Three options for encapsulation are allowed for

Mobile IP:

IP-within-IP encapsulation: IP datagram is inserted into a

new IP datagram with the care-of address.

Minimal Encapsulation:Less overhead, only a few fields

are added in the outer datagram.

Generic routing encapsulation (GRE): This is a generic

encapsulation procedure that was developed prior to the

development of Mobile IP


36/44

Operation of Mobile IP

IP datagram to A

Encapsulation and Tunnelling

Network Level PDU

As response travels directly

to X due to fixed IP of X


37/44

Lecture 5: Mobility

Mobile IP

RFC 3344

has many features weve seen:

home agents, foreign agents, foreign-agent

registration, care-of-addresses, encapsulation(packet-within-a-packet)

three components to standard:

indirect routing of datagrams

agent discovery

registration with home agent

37


38/44

Features of Mobile IP

The mobile IP architecture comprises three functions:

1. A database that contains the most up-to-date mapping between the

two address spaces (home address to care-of-address)

2. The translation of the host identifier to the actual destination

address

3. Agents ensuring that the source and destination packets for arriving

and outgoing packets are updated properly so that routing of

packets are proper


39/44

Mobile IP

Whenever the mobile host moves to a new subnet managed by a different

foreign agent, the dynamic care-of-address will change.

This changed care-of-address needs to be communicated to the home agent.

This process works for slowly moving hosts. For a high speed mobile host, therate of update of the addresses needs to match the rate of change of ddresses.

Otherwise, packets will be forwarded to the wrong (old) address.

Mobile IP fails to update the addressed properly for high speed mobility.

Cellular IP a new host mobility protocol has been designed to address this

issue.


40/44

Mobile IP Vs Cellular IP


41/44

41

Example: Boeing Connexion Service

Internet

12.78.3.0/24
http://www.freedigitalphotos.net/albums/userpics/10001/airplane6.jpghttp://www.lbisat.com/gallery/photos/New%20Skies%20Satellite.jpghttp://www.lbisat.com/gallery/photos/New%20Skies%20Satellite.jpghttp://www.esa.int/spacecraftops/Image/urlpicturelarge_id_1069167511889_NNO_new_l,2.jpghttp://www.esa.int/spacecraftops/Image/urlpicturelarge_id_1069167511889_NNO_new_l,2.jpg


42/44

Security in Mobile IP

Authentication can be performed by all parties

Only authentication between MN and HA is required

Keyed MD5 is the default

Replay protection

Timestamps are mandatory

Random numbers on request reply packets are optional

HA and FA do not have to share any security information.


43/44

Problems with Mobile IP

Suboptimal triangle routing

What if MN is in same subnetwork as the node to which it is communicating andHA is on the other side of the world?

It would be nice if we could directly route packets

Solution: Let the CN know the COA of MN

Then the CN can create its own tunnel to MN

CN must be equipped with software to enable it to learn the COA

Initiated by HA who notifies CN via binding update

Binding table can become stale

Single HA model is fragile

Possible solutionhave multiple HA

Frequent reports to HA if MN is moving

Possible solutionsupport of FA clustering

Security

Connection hijacking, snooping

Many open research questions


44/44

Mobility in IPv6

Route Optimization is a fundamental part of Mobile IPv6

Mobile IPv4 it is an optional set of extensions that may not be supported by allnodes

Foreign Agents are not needed in Mobile IPv6

MNs can function in any location without the services of any special router in thatlocation

Security

Nodes are expected to employ strong authentication and encryption

Other details

mc-6 mobile ip

Documents